Thomas spencer miller



(No Model.)

T. s. MILLER.

ROPE TRANSMISSION.

No. 444,919. Patented M11520, 1891.- v

UNITED STATES ATENT rmcn.

THOMAS SPENCER MILLER, OF NEIV YORK, N. Y.

ROPE TRANSMISSION.

SPECIFICATION forming part of Letters Patent No. 444,919, dated January20, 1891.

Application filed August 6, 1890- Serial No.- 36l,225. (N0 model.)

To all whom it may concern:

Be it known that I, THOMAS SPENCER MIL- LER, of New York, in the countyand State of New York, have in vented a new and useful Improvement inRope Transmission, of which the following is a specification.

I believe that my invention finds its greatest utility in the connectionwith what I will call continuous-rope transmission, or, in other words,transmission which is accomplished by a continuous rope wound insuccessive coils around two grooved sheaves and taking one turn around athird sheave designed to maintain the required tension. Heretofore ithas been found in practice that in transmission of this character somemembers or strands of the coil will run under a different tension fromothers, to such an extent, in fact, that certain of the members will bevery obviously slack, and this has been one objection raised to thissystem of transmission.

lhe object of my invention is to overcome this difficulty, which Ibelieve to have been discovered to be due to the difference in diameterbetween the driving and the driven sheave, as the same are generallyemployed, causing a difference in the are of contact between the coilsupon one sheave and that upon the other, the arc of contact on thesmaller sheave being less than the are of con tact on the larger sheave.This dilference in the arc of contact, I believe, will cause adifference in the friction, so that the members of the coil are drivenby the larger sheave with a greater capacity of power than by thesmaller sheave. I propose to compensate for the difference abovereferred to, and thereby pro duce a balance of forces, as exists in thecase where the sheaves employed are of equal diameters, so that anequality of tension is preserved throughout the various members ofthecoil, and this compensation I propose to accomplish by the adjustmentof the relative form existing between-the grooves of the respectivesheaves in the manner hereinafter more particularly described.

In the drawings, Figure 1 represents a sectional elevation in an axialdirection of two sheaves and connecting-coils on the line as as of Fig.2. Fig. 2 represents the same thing from a direction at right angles tothe axis.

Figs. 3 and 4 represent a cross-section of the grooves on the twosheaves, showing a relationship which will embody my invention, saidsections being taken, respectively, on the lines 3 y and z 2 of Fig. 1.

a (L is the main driving-sllal't.

b is the driving pulley or sheave.

c is the driven shaft, and d the driven pulley or sheave.

e is the tension-wheel, which is journaled in a carriage f, mounted 011a track g, and the tension is obtained by any suitable device, such asthe chain 7L and weight 7;, connected with the carriage.

7c is the endless rope by which the power is transmitted. Starting atthe tension-wheel e, this rope proceeds around the first groove in thesheave b, thence around the first groove in the sheave d, thence aroundthe second groove in the sheave Z), and so on in succession around allof the grooves in the sheaves b and (Z. After passing around the lastgroove in the sheave d the rope passes around a groove in a sheave l,which is placed side by side with the sheave b, but is loose on theshaft a. From this loose sheave the rope passes back to the tensionwheel6, where it started. The driving-sheave b is larger in diameter than thedriven sheave d, and if the grooves in these two wheels were alike inform some laps in the rope coil would be under greater tension thanothers. In order to overcome this difficulty, I form the grooves m ofthe sheave (Z so that the sides thereof form a more acute angle witheach other than those of grooves q of the sheave Z). Thus the sides maand m o of the grooves in the sheave cZ,Fig. 4:, are shown as forming anangle of sixty degrees with each other, whereas the sides pg and qr ofthe grooves in the sheave I) are shown as forming an angle of ninetydegrees with each other. Of course I merely mention these particularangles to show, in general, a form of construction which will answerwell for carrying out my invention, and I do not thereby intend to limitmyself to the angles shown, since the principle of my invention is tomake the an gle of the sheave of smaller diameter, more acute than theangle of the grooves of the sheave of larger diameter. The presence ofthe loose sheave Z will enable the parts to adjust themselves tovariations requiring the operation of the tension-Wheel withoutproducing the slip which would otherwise occur in the groove of thedriving-sheave b.

In addition to the advantages already pointed out, the making of thegrooves in one of the pulleys a more obtuse angle produces a conditionof things favoring the durability of the rope employed.

I have described the adoption of ditferent angles for the grooves of thetwo sheaves employed as applied to rope-transmission by a singlecontinuous rope; but I do not Wish, unless so specified in the claims,to limit myself to this application; nor do I desire to limit myself tothe other forms of construction in which my invention is embodied, asabove set forth.

I claim- 1. In combination with a continuous powertransmitting rope, adriving-sheave, a driven sheave of different diameter, and a tension-Wheel, the grooves in the sheave of greater diameter forming a moreobtuse angle than the grooves in the sheave of lesser diameter,substantially as described.

2. In combination with a power-transmitting rope, a driving-sheave, adriven sheave, an idler-Wheel, and a tension-wheel, the driving-sheaveand driven sheave being of different diameters, and the grooves in thesheave of greater diameter being of a more obtuse angle than the groovesof the sheave of lesser diameter, substantially as described.

3. In combination, a driving-sheave, a driven sheave of differentdiameter, and a powertransmitting rope, the said sheaves being providedwith grooves, those of the larger sheave having a more obtuse angle thanthe grooves of the smaller sheave, substantially as described.

THOMAS \Vitnesses;

JAMES '1. LAW, FRED KEMPER.

SPENCER I LLER.

